Purification and Characterisation of Organic Compounds

What is Purification and Characterisation of Organic Compounds

In this purification and characterization of organic compounds chapter, there are various important methods and techniques like sublimation, chromatography, distillation, etc to purify the organic compounds. Once an organic compound is synthesized, it is mandatory to purify it. Depending upon the nature of the organic compound and the impurities, a particular technique is used to purify it. In sublimation, the compound is directly converted into vapour and thus separated and purified. In crystallization, a compound is cooled and make into crystal form and thus purified. In distillation, a compound is heated and converted into vapour and thus separated. In chromatography, with the help of stationary and mobile phase, the compounds are purified.

The various techniques used in this chapter have various real-life applications that we see in our daily life. Some of them are mentioned below.

Chromatography is also used for purification of biomolecules like proteins, RNA and DNA.

Mothballs are used to take away moths and other insects. These balls are made of naphthalene.

Notes for purification and characterisation of organic compounds

In this section, you will study about the important topics of the chapter, overview, purification methods and some important tips and guidelines for the preparation of the chapter at the best.

Important Topics - Purification and Characterisation of Organic Compounds

Sublimation

Crystallization

Distillation

Differential extraction

Chromatography

Overview of the Chapter- Purification and Characterization of Organic Compounds

In this chapter, you will learn about the various important methods and techniques to purify organic compounds. After getting the organic compounds either from a natural source or by synthesizing in the laboratory, it is always mandatory to purify these compounds. There are various methods available for purification of organic compounds according to the nature of these compounds. Some common major methods of purification are given as below.

(i) Sublimation: This is the process in which a solid is directly converted into its vapour state by heating without passing it through the liquid state. For example, camphor is the substance that gets converted into its vapour state directly on heating. Thus all those organic compounds that are sublimable, can be purified and separated from non-sublimable impurities by this technique.

(ii) Crystallisation: This is the process in which the compound and impurities are separated from each other based on their solubility in the solvent. The impurities are little soluble in the solvent at lower temperatures and but highly soluble at higher temperatures. Thus, after dissolving the compound and the impurities at higher temperatures, now the solution is cooled to very low temperatures. In this way, the compound crystallizes and the impurities are still in the solvent. Thus, the compound is separated by filtration and the impurities are discarded. This process is done multiple times to the purify the compound to the highest level.

(iii) Distillation: In this process, only those components are separated which significant difference in their boiling points. In this process, compounds mixture is present in the round flask as shown in the figure. Now, this flask is heated and the component that has a lower boiling point starts to vapourise. These vapours are first condensed and then are collected separately. Now, if we want to boil the other component as well, then we increase the temperature further but by now, we have already separated and purified our components.
Distillation is done in two ways:

Fractional distillation

Steam distillation

(iv) Differential Extraction: This is the technique which we use to purify the organic compound which is present in the aqueous solvent. Basically, when an organic compound is present in an aqueous solvent then we add one more organic solvent in the funnel and then shake it. The compound is more soluble in organic solvent thus it is collected in the organic solvent phase. In this process, the two solvents i.e, aqueous and organic are immiscible with each other. The organic solvent is later removed by distillation or by evaporation to get the compound. If the organic compound is less soluble in an organic solvent, then we have to add a large amount of organic solvent to dissolve the compound completely.

(v) Chromatography: Chromatography is a very important widely used technique to separate and purify the components. In this technique, different components are adsorbed on the stationary phase. Now a mobile phase is allowed to pass through the column and thus the different components are separated. The chromatography technique is further subdivided into two various categories:

(a) Adsorption Chromatography: In this category, the different components are adsorbed on the adsorbent column. Usually, the adsorbents used in chromatography are silica or alumina. Now a mobile phase is passed through the stationary column. This mobile phase takes with it either the impurities or the desired compound, depending upon the properties of the compound and the mobile phase. Thus, in this way the components are separated and purified.

Adsorption chromatography is further subdivided into two categories viz:

Column chromatography

Thin-layer chromatography

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(b) Partition Chromatography: In this chromatographic technique, the different components are separated from each other depending upon their property and the properties of the stationary phase and the mobile phase. Paper chromatography is a type of partition chromatography. In paper chromatography, a paper known as chromatography paper is used. In this paper, water is already trapped and act as a stationary phase. Now, this chromatography paper is dipped in a solution of different components. Now, the solvent rises up by the capillary action. Thus, on the paper, different components stop at different heights depending upon their individual properties, stationary phase and the solvent. These spots can be easily observed under ultraviolet light.

How to prepare for Purification and Characterisation of Organic Compounds

This chapter is part of organic chemistry. This chapter basically covers all the important techniques that we use to purify the compounds.

For preparing this chapter, there is no need for any pre-requisite chapter. Thus prepare it freshly and actively.

In this chapter, chromatography is one such important technique that we do in our labs also in our graduation. It is a very interesting technique.

In the nutshell, it can be said that although this chapter is not very long, it is a very simple and straightforward one. So always say a "Big YES" to this chapter.

Prescribed Books

For this chapter, first, the NCERT book is best for initial level preparation as well as for board exams. Now, after this, if you want to prepare for competitive exams like JEE and NEET, then these are the best books for you - O.P Tandon. Meanwhile, in the preparation, you must continuously give the mock tests for the depth of knowledge. Our platform will help you to provide with the variety of questions for deeper knowledge with the help of videos, articles and mock tests.